Anti-coronavirus and anti-pulmonary inflammation effects of iridoids, the common component from Chinese herbal medicines for the treatment of COVID-19.

The practice of Chinese herbal medicines for the treatment of COVID-19 in China played an essential role for the control of mortality rate and reduction of recovery time. The iridoids is one of the main constituents of many heat-clearing and detoxifying Chinese medicines that were largely planted and frequently used in clinical practice. Twenty-three representative high content iridoids from several staple Chinese medicines were obtained and tested by a SARS-CoV-2 pseudo-virus entry-inhibition assay on HEK-293 T/ACE2 cells, a live HCoV-OC43 virus infection assay on HRT-18 cells, and a SARS-CoV-2 3CL protease inhibitory FRET assay followed by molecular docking simulation. The anti-pulmonary inflammation activities were further evaluated on a TNF-α induced inflammation model in A549 cells and preliminary SARs were concluded. The results showed that specnuezhenide (7), cornuside (12), neonuezhenide (15), and picroside III (21) exhibited promising antiviral activities, and neonuezhenide (15) could inhibit 3CL protease with an IC50 of 14.3 µM. Docking computation showed that compound 15 could bind to 3CL protease through a variety of hydrogen bonding and hydrophobic interactions. In the anti-pulmonary inflammation test, cornuside (12), aucubin (16), monotropein (17), and shanzhiside methyl ester (18) could strongly decrease the content of IL-1ß and IL-8 at 10 µM. Compound 17 could also upregulate the expression of the anti-inflammatory cytokine IL-10 significantly. The iridoids exhibited both anti-coronavirus and anti-pulmonary inflammation activities for their significance of existence in Chinese herbal medicines, which also provided a theoretical basis for their potential utilization in the pharmaceutical and food industries.

Key role of hydrogen atoms in the preparation of sulfidated zero valent iron.

Sulfidated zero valent iron (ZVI) is a popular material for the reductive degradation of halogenated organic pollutants. Simple and economic synthesis of this material is highly demanded. In this study, sulfidated micro/nanostructured ZVI (MNZVI) particles were prepared by simply heating MNZVI particles and sulfur elements (S0) in pure water (50℃). The iron oxides on the surface of MNZVI particles were conducive to sulfidation reaction, indicating the formation of iron-sulphide minerals (FeSx) on the surface of MNZVI particles might not be from the direct reaction of Fe0 with S0 (Fe0 and S0 acted as reductant and oxidant, respectively). As an important reductant, hydrogen atom (H•) can be generated from the reduction of H+ by MNZVI particles and participate in the formation of FeSx. Quenching experiment and cyclic voltammetry analysis proved the existence of H• on the surface of MNZVI particles. DFT calculation found that the potential barrier of H•/S0 and Fe0/S0 were 1.91 and 7.24 eV, respectively, indicating that S0 would preferentially react with H• instead of Fe0. The formed H• can quickly react with S0 to generate hydrogen sulfide (H2S), which can further react with iron oxides such as α-Fe2O3 on the surface of MNZVI particles to form FeSx. In addition, the H2 partial pressure in water significantly affected the amount of H• generated, thereby affecting the sulfidation efficiency. For TCE degradation, as the sulfur loading of sulfidated MNZVI particles increased, the contribution of H• significantly decreased while the contribution of direct electron transfer increased. This study provided new insights into the synthesis mechanism of sulfidated ZVI in water.

Lignan glucosides from Gentiana macrophylla with potential anti-arthritis and hepatoprotective activities.

Ten lignans, including six previously undescribed phenolic ester glycosyl lignans (1-6), were isolated from a well-known traditional Chinese medicine, Qin-Jiao, which is the dry root of Gentiana macrophylla Pall. (Gentianaceae). Their structures were determined by spectroscopic and chemical methods, especially 2D NMR techniques. Quantum chemical calculations of theoretical ECD spectra allowed the determination of their absolute configurations. Refer to its traditional applications for the treatment of rheumatic arthralgia and hepatopathy, these compounds were evaluated on a TNF-α induced MH7A human synoviocyte inflammation model and a D-GalN induced AML12 hepatocyte injury model. Compounds 1, 2, 5, and 6 significantly reduced the release of proinflammatory cytokine IL-1ß in MH7A cells at 15 µM and they also could strongly protect AML12 cells against D-GalN injury at 30 µM. Flow cytometry and Western blot analysis showed that compound 5 ameliorated D-GalN induced AML12 cell apoptosis by upregulating the expression of anti-apoptotic Bcl-2 protein and down-regulating the expression of pro-apoptotic Bax protein.

Dynamic Production of Hydroxyl Radicals during the Flooding-Drainage Process of Paddy Soil: An In Situ Column Study.

Frequent cycles of flooding and drainage in paddy soils lead to the reductive dissolution of iron (Fe) minerals and the reoxidation of Fe(II) species, all while generating a robust and consistent output of reactive oxygen species (ROS). In this study, we present a comprehensive assessment of the temporal and spatial variations in Fe species and ROS during the flooding-drainage process in a representative paddy soil. Our laboratory column experiments showed that a decrease in dissolved O2 concentration led to rapid Fe reduction below the water-soil interface, and aqueous Fe(II) was transformed into solid Fe(II) phases over an extended flooding time. As a result, the •OH production capacity of liquid phases was reduced while that of solid phases improved. The •OH production capacity of solid phases increased from 227-271 µmol kg-1 (within 1-11 cm depth) to 500-577 to 499-902 µmol kg-1 after 50 day, 3 month, and 1 year incubation, respectively. During drainage, dynamic •OH production was triggered by O2 consumption and Fe(II) oxidation. ROS-trapping film and in situ capture revealed that the soil surface was the active zone for intense H2O2 and •OH production, while limited ROS production was observed in the deeper soil layers (>5 cm) due to the limited oxygen penetration. These findings provide more insights into the complex interplay between dynamic Fe cycling and ROS production in the redox transition zones of paddy fields.

Amendment of organic acids significantly enhanced hydroxyl radical production during oxygenation of paddy soils.

Recently, hydroxyl radical (•OH) production during soil redox fluctuations has been increasingly reported, but the low efficiency of contaminant degradation is the barrier for engineering remediation. The widely distributed low-molecular-weight organic acids (LMWOAs) might greatly enhance •OH production due to their strong interactions with Fe(II) species, but it was less investigated. Herein, we found that LMWOAs amendment (i.e., oxalic acid (OA) and citric acid (CA)) significantly enhanced •OH production by 1.2 -19.5 times during oxygenation of anoxic paddy slurries. Compared with OA and acetic acid (AA) (78.4 -110.3 µM), 0.5 mM CA showed the highest •OH accumulation (140.2 µM) due to the elevated electron utilization efficiency derived from its strongest capacity for complexation. Besides, increasing CA concentrations (within 6.25 mM) dramatically enhanced the •OH production and imidacloprid (IMI) degradation (increased by 48.6%), and further decreased due to the extensive competition from excess CA. Compared to 0.5 mM CA, the synergistic effects of acidification and complexation induced by 6.25 mM CA rendered more formation of exchangeable Fe(II) that easily coordinated with CA, and thus significantly enhanced its oxygenation. This study proposed promising strategies for regulating natural attenuation of contaminants using LMWOAs in agricultural fields, especially soils with frequent occurrence of redox fluctuations.

Rapid determination and health risk assessment of neonicotinoids in source water and tap water of the tropical Hainan Island, China.

Neonicotinoids (NEOs) pesticides are widely used around the world, especially in the tropics with greater frequency and intensity. However, little is known about NEOs residue in drinking water of tropics. In this study, a highly efficient method using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established for determining eight NEOs in source water and tap water of Hainan Island, China. The method adopted a high-throughput direct aqueous injection without sample concentration steps, with a rapid analyzing period of 5.0 min, method detection limits (MDLs) in the range of 0.84-1.82 ng/L and the average recoveries ranged from 83% to 116%. NEOs were detected in all source water samples and at an upper level as compared with other parts of China. The most frequently detected NEO was imidacloprid with a detection frequency of 94%, followed by clothianidin (88%) and thiamethoxam (78%), with maximum concentrations of 86.4, 164, and 188 ng/L, respectively. Moreover, seasonal and spatial variations had remarkable impacts on NEO contamination in source water. Drinking water treatment processes removed approximately 20% of NEOs from surface water. However, 90% of tap water samples contained at least one NEO, With 3 samples' concentration of single NEO exceeding the acceptable value recommended by the European Union (100 ng/L). Therefore, the risk of human exposure through drinking water was evaluated for 4 age group and 2 genders. Young children aged 9 months to 3 years old were found to have the highest risk, with the median exposure up to 4 times greater than teenagers and adults. Next, water intake is likely only a small part of the daily intake of these individuals, thus the potential health problems caused by NEOs present in the tap water of Hainan should not be ignored.

Effect of metal cations on antimicrobial activity and compartmentalization of silver in Shewanella oneidensis MR-1 upon exposure to silver ions.

Silver is an antimicrobial agent that is used extensively in consumer products, such as fabrics and humidifiers. Silver ion (Ag+) uptake in bacteria represents a crucial phase of antimicrobial activity. However, the uptake mechanism of Ag+ in bacteria remains largely unknown. The genus Shewanella drives many geochemical processes of nutrients and pollutants in soils. In the present study, Ag+ uptake by Shewanella oneidensis MR-1 was first investigated in a laboratory in defined anaerobic, oligotrophic, and inorganic media with or without cations (potassium ions [K+], magnesium ions [Mg2+], and zinc ions [Zn2+]). Our results revealed variations in antimicrobial activity of Ag+ in the presence of Mg2+ and Zn2+. First, Mg2+ significantly decreased antimicrobial activity of Ag+ in S. oneidensis MR-1 by inhibiting cellular Ag+ uptake when compared with K+. The results were consistent with that of Co2+ (Mg2+ channel blocker) decreased Ag+ uptake by S. oneidensis MR-1. Moreover, Mg2+ promoted riboflavin secretion and facilitated the formation of metallic Ag nanoparticles on bacterial surfaces, which was beneficial for extracellular electron transfer and consequently reduced antibacterial activity of Ag+. Second, Zn2+ increased the antimicrobial activity of Ag+ in S. oneidensis MR-1, although the effect on Ag+ uptake was minimal. A synergistic interaction between Zn2+ and Ag+ led to an increase in dead cells and decreased ferrihydrite reduction capacity. The findings suggest that Mg2+ could reduce the environmental risk of Ag+ to soil bacteria, while Zn2+ should be of particular concern due to its synergistic antimicrobial effect on bacteria.

Hydroxyl radical formation during oxygen-mediated oxidation of ferrous iron on mineral surface: Dependence on mineral identity.

Many studies have examined the redox behavior of ferrous ions (Fe(II)) sorbed to mineral surfaces. However, the associated hydroxyl radical (•OH) formation during Fe(II) oxidation by O2 was rarely investigated at circumneutral pH. Therefore, we examined •OH formation during oxygenation of adsorbed Fe(II) (Fe(II)sorbed) on common minerals. Results showed that 16.7 ± 0.4-25.6 ± 0.3 µM of •OH was produced in Fe(II) and α/γ-Al2O3 systems after oxidation of 24 h, much more than in systems with dissolved Fe(II) (Fe2+aq) alone (10.3 ± 0.1 µM). However, •OH production in Fe(II) and α-FeOOH/α-Fe2O3 systems (6.9 ± 0.1-8.3 ± 0.1 µM) slightly decreased compared to Fe2+aq only. Further analyses showed that enhanced oxidation of Fe(II)sorbed was responsible for the increased •OH production in the Fe(II)/Al2O3 systems. In comparison, less Fe(II) was oxidized in the α-FeOOH/α-Fe2O3 systems, which was probably ascribed to the quick electron-transfer between Fe(II)sorbed and Fe(III) lattice due to their semiconductor properties and induced formation of high-crystalline Fe(II) phases that hindered Fe(II) oxidation and •OH formation. The types of minerals and solution pH strongly affected Fe(II) oxidation and •OH production, which consequently impacted phenol degradation. This study highlights that the properties of minerals exert great impacts on surface-Fe(II) oxidation and •OH production during water/soil redox fluctuations.

Biotic Process Dominated the Uptake and Transformation of Ag+ by Shewanella oneidensis MR-1.

Silver ions (Ag+) directly emitted from industrial sources or released from manufactured Ag nanoparticles (AgNPs) in biosolid-amended soils have raised concern about the risk to ecosystems. However, our knowledge of Ag+ toxicity, internalization, and transformation mechanisms to bacteria is still insufficient. Here, we combine the advanced technologies of hyperspectral imaging (HSI) and single-particle inductively coupled plasma mass spectrometry to visualize the potential formed AgNPs inside the bacteria and evaluate the contributions of biological and non-biological processes in the uptake and transformation of Ag+ by Shewanella oneidensis MR-1. The results showed a dose-dependent toxicity of Ag+ to S. oneidensis MR-1 in the ferrihydrite bioreduction process, which was primarily induced by the actively internalized Ag. Moreover, both HSI and cross-section high-resolution transmission electron microscopy results confirmed that Ag inside the bacteria existed in the form of particulate. The Ag mass distribution in and around live and inactivated cells demonstrated that the uptake and transformation of Ag+ by S. oneidensis MR-1 were mainly via biological process. The bioaccumulation of Ag+ may be lethal to bacteria. A better understanding of the uptake and transformation of Ag+ in bacteria is central to predict and monitor the key factors that control Ag partitioning dynamics at the biointerface, which is critical to develop practical risk assessment and mitigation strategies.

Extensive production of hydroxyl radicals during oxygenation of anoxic paddy soils: Implications to imidacloprid degradation.

Hydroxyl radical (•OH) plays a critical role in driving organic pollutants degradation during redox fluctuations. Such processes have been frequently investigated in sedimentary environments, but rarely referred to the agricultural fields, such as paddy soils with frequent occurrence of redox fluctuations. Our findings demonstrated that extensive •OH (40.3-1061.4 µmol kg-1) was produced during oxygenation of anoxic paddy slurries under circumstance conditions. Wet chemical sequential extractions, Mössbauer spectra, and X-ray photoelectron spectroscopy characterizations collectively corroborated that 0.5 M HCl-extracted Fe(II) (i.e., surface-bound Fe and Fe in low-crystalline minerals) contributed to more •OH production than aqueous Fe2+. The produced •OH can efficiently induce the oxidative transformation of organic carbon and the degradation of imidacloprid (IMP), which in turn produced the by-products, such as IMP-urea, IMP-olefin, and 6-chloronicontinic acid, via •OH-attacking mechanisms. Quenching experiments showed that hydrogen peroxide (H2O2) was the important intermediate for •OH formation via Haber-Weiss mechanisms during oxygenation processes. These findings indicate that abundant •OH can be produced during the redox fluctuations of paddy soil, which might be of great significance to predict the removal of organic contaminants and the mineralization of organic carbon in paddy fields.

Two new 2,5-diketopiperazine derivatives from mangrove-derived endophytic fungus Nigrospora camelliae-sinensis S30.

Two new 2,5-diketopiperazines derivatives (1-2), together with eight known analogs (3-10), were isolated from a culture broth of an endophytic fungus Nigrospora camelliae-sinensis S30, derived from mangrove Lumnitzera littorea. Their complete structures were determined by a detailed analysis of spectroscopic data and ECD calculations. The antimicrobial activity and neuroprotective activity of these isolated compounds were also evaluated.

Active iron species driven hydroxyl radicals formation in oxygenation of different paddy soils: Implications to polycyclic aromatic hydrocarbons degradation.

The frequently occurring redox fluctuations in paddy soil are critical to the cycling of redox-sensitive elements (e.g., iron (Fe) and carbon) due to the driving of microbial processes. However, the associated abiotic process, such as hydroxyl radical (•OH) formation, was rarely investigated. Hence, we examined the under-appreciated role of •OH formation in driving polycyclic aromatic hydrocarbons (PAHs) degradation upon oxygenation of anoxic paddy slurries. Results showed that •OH production largely differed in different paddy slurries, in the range of 271.5-581.2 µmol kg-1 soil after 12 h reaction. The •OH production was highly hinged on the contents of active Fe species, i.e., exchangeable, surface-bound Fe and Fe in low-crystalline phases rather than Fe in high-crystalline minerals or silicates. Besides, •OH production significantly decreased with increasing soil depth due to the declined active Fe species and abundance of functional microbes. Oxygenation also induced the transformation of these active Fe species into the low- and high-crystalline phases, which might affect the following redox process. The produced •OH can efficiently degrade PAHs with degradation extents depending on their physiochemical properties. Our findings highlight the key roles of active Fe species in driving •OH formation and organic contaminants degradation during redox fluctuations of paddy soils.

Pyrogenic Carbon Initiated the Generation of Hydroxyl Radicals from the Oxidation of Sulfide.

Sulfide is one of the most abundant reductants in the subsurface environment, while pyrogenic carbon is a redox medium that widely exists in sulfide environment. Previous studies have found pyrogenic carbon can mediate the reductive degradation of organic pollutants under anoxic sulfide conditions; however, the scenario under oxic sulfide conditions has rarely been reported. In this study, we found that pyrogenic carbon can mediate hydroxyl radicals (•OH) generation from sulfide oxidation under dark oxic conditions. The accumulated •OH ranged from 2.07 to 101.90 µM in the presence of 5 mM Na2S and 100 mg L-1 pyrogenic carbon at pH 7.0 within 240 min. The Raman spectra and electrochemical cell experiments revealed that the carbon defects were the possible chemisorption sites for oxygen, while the graphite crystallites were responsible for the electron transfer from sulfide to O2 to generate H2O2 and •OH. Quenching experiments and degradation product identification showed that As(III) and sulfanilamide can be oxidized by the generated •OH. This research provides a new insight into the important role of pyrogenic carbon in redox reactions and dark •OH production.

The overlooked oxidative dissolution of silver sulfide nanoparticles by thermal activation of persulfate: Processes, mechanisms, and influencing factors.

The widely occurring silver sulfide nanoparticles (Ag2S-NPs) are regarded as stable Ag species in subsurface environments, where are often disturbed by human activities, such as the application of advanced oxidation technologies (e.g. persulfate based in situ chemical oxidation (PS-ISCO)) in the remediation of contaminated soil and groundwater. However, stability of Ag2S-NPs was rarely investigated referring to these processes. Here, we systematically investigated the dissolution process of Ag2S-NPs in thermal activation of PS system. Results showed that dissolution of Ag2S-NPs fitted the pseudo-first-order kinetics and the kobs increased from 0.017 h-1 to 0.249 h-1 with increasing PS concentration from 2 mM to 10 mM (36 h, 40 °C). Quenching experiments and EPR results showed that sulfate radical (SO4•-) and hydroxyl radical (•OH) were the dominant oxidants in inducing the oxidative dissolution of Ag2S-NPs. XPS analysis showed that surface-bound S2- in Ag2S-NPs was oxidized and transformed into aqueous sulfur species. The released Ag+ may also act as effective catalysts to activate PS and therefore promote the oxidation process. These findings suggest that stability of Ag2S-NPs should be reevaluated to better understand its risk to the ecological system in the subsurface environment where ISCO was widely applied.

Photochemical behavior of benzophenone sunscreens induced by nitrate in aquatic environments.

Benzophenones (BPs), which are widely used UV filters, have aroused considerable public concern owing to their potential endocrine-disrupting activities. Herein, we systematically investigated their photochemical behavior and fate, which is mediated by nitrate in aquatic environments. The results showed that 10 µM of 3 BPs can be completely degraded within 4 h of simulated sunlight irradiation in a 10 mM nitrate solution at pH 8.0, and 2,4-dihydroxybenzophenone (BP-1) has a 31.6% mineralization rate after 12 h irradiation. Their photolytic rates (kobs) presented a significant linear correlation with the logarithmic values of the nitrate concentration for 0.1-10 mM (R2 > 0.98), and in three actual waters, the rates of BP-1 were also positively related to the intrinsic nitrate concentration. Furthermore, higher transformation rates under alkaline condition were observed, especially for BP-1, with its kobs at pH 10 being 8.3-fold higher than that at pH 6.0. Moreover, dissolved oxygen (DO) also has an impact on the reaction kinetics to some degree. According to the quenching experiments, we found that three reactive oxygen species (ROS), namely, •OH, •NO, and •NO2, participated in this photolysis of BPs, and the contribution of •OH accounted for 32.1%. Furthermore, we selected BP-1 as the model molecule to study the transformation pathways and toxicity changes in this system. Four main transformation pathways including hydroxylation, nitrosylation, nitration, and dimerization were proposed, based on liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) analysis and density functional theory (DFT). According to the toxicity test, the formed intermediates were more toxic to Photobacterium phosphoreum than the parent BP-1. Therefore, these results can help reveal primary phototransformation mechanisms and evaluate the potential ecological risks of BPs in aquatic environments.